This project seeks to improve the current methods of labeling leukocytes and platelets with gamma-emitting agents for the delineation of focal inflammatory lesions, endothelial injury and thrombi by scintillation camera imaging. New radiopharmaceuticals will be developed, including analogues of 8-hydroxyquinoline, disulphide compounds and bis-thiosemicarbazones. These lipophilic chelating agents will be labeled with 99mTc, 111In, 197Hg, 203Pb or 97Ru. A continuous flow elutriation system with a special centrifuge rotor will be used to harvest leukocytes and centrifugation with Metrizamide or Stractan density gradients will be used to harvest platelets. Viability of the isolated labeled cells will be assessed by reinjection into experimental animals and measurement of cell recovery and survival in the blood stream. Their efficacy in demonstrating focal inflammatory lesions and vascular damage will be assessed in animals by gamma camera imaging and by direct tissue radioassay.